1. Field of the Invention
The present invention relates to metal-in-gap (MIG) ferrite magnetic heads. In particular, the present invention relates to an improved MIG head having a thin barrier layer of tungsten or tantalum for suppression of secondary pulse effects.
2. Description of the Prior Art
The advent of high coercivity magnetic media has led to a renewed interest in metal-in-gap (MIG) ferrite magnetic heads In a metal-in-gap ferrite magnetic head, a layer of high magnetic moment material is deposited on the trailing edge core face to achieve improved write characteristics and consequently higher linear recording density. Improved read characteristics are achieved by use of a layer of high magnetic moment material on one or both core faces.
In one typical configuration, the ferrite cores are Mz-Zn ferrite, and the high magnetic moment material deposited on the core faces of the ferrite is an Fe-Si-Al based alloy known as Sendust.
It has been discovered that MIG heads exhibit a so-called "secondary electrical pulse", which appears to be produced at the location of the ferrite-metal interface. This is believed to be due to a chemical reaction between the metal (e.g., Sendust) and the ferrite (e.g., Mn-Zn ferrite) resulting in a magnetically dead reaction layer (i.e., a "secondary gap" or "pseudo gap") between the ferrite and the high magnetic moment metal. In Kajiwara et al, "Auger Spectroscopy Analysis of Metal/Ferrite Interface Layer in Metal-In-Gap Magnetic Gap", Intermag/MMM Conference, Vancouver, B.C., paper EE-11 (1988), it was reported that when the metal was Sendust, the reaction layer which apparently produces the secondary pulse is composed of Al.sub.2 0.sub.3 and SiO.sub.2. In addition, Kajiwara et al reported that using another high magnetic moment metal (an Fe-Ga-Si-Ru alloy) instead of Sendust resulted in a reaction layer composed of Ga.sub.2 O.sub.3 and SiO.sub.2. To reduce the secondary pulse problem, Kajiwara et al suggested the use of a thin silicon dioxide or silicon oxynitride barrier layer between the ferrite and the metal. It was reported by Kajiwara et al that these barrier layers reduced reaction between the metal and the Mn-Zn ferrite. The barrier layers appeared to be more efective when the metal was Fe-Ga-Si-Ru alloy than when the metal was Sendust.
The problem of the secondary gap in a metal-in-gap head was also discussed in Sillen et al, "Permalloy/Sendust Metal-In-Gap Head" IEEE Trans. On Mag., Vol. 24, No. 2, pp. 1802-1804 (1988), and in the Enz et al U.S. Pat. No. 4,764,832. The proposed solution in both of these references is a layer of permalloy (NiFe) between the ferrite core face and the Sendust layer. The thickness of this permalloy layer is between 500 and 20,000 Angstroms.
Eckstein U.S. Pat. No. 4,704,788 discusses the problem of pseudo gaps at the interface between the ferrite core and the Sendust layer of a MIG head. The Eckstein patent suggests a method of fabrication which includes depositing a thin adhering layer over the ferrite before depositing the Sendust alloy layer. The Eckstein patent does not disclose, however, the composition of the thin adhering layer.
Gorter et al U.S. Pat. No. 4,670,807 shows a MIG head and indicates that there are transition zones between each of the ferrite cores and the corresponding Sendust layers. The Gorter et al. patent suggests modifying relative thicknesses of the Sendust layers to achieve better frequency response. It is also suggested that transition zones be made of glass or titanium to serve for better bonding between the ferrite cores and the Sendust layers.
Kuriyama U.S. Pat. Nos. 4,742,412 and 4,768,118 describe MIG heads having a thin layer of chromium or titanium between a Sendust layer and a trailing ferrite core. This thin layer is between 200 to 500 Angstroms in thickness.
There is a continuing need for improved MIG heads which offer better suppression of secondary pulse phenomena than has been possible with the prior art approaches.